German Standard Problem No. 7: 'Behavior of a fuel rod bundle during a specified heat-up and flooding period'

The pretest-predictions of the thermo-mechanical behaviour of certain preselected fuel rods utilizing some measured thermohydraulic cooling parameters were successfully performed. Scatter of predicted internal fuel rod pressures and local strains was slightly larger compared to that of measured values. Without decoupling the prediction of the thermomechanic behaviour from the prediction of the thermohydraulic behaviour the requested high accuracy of local temperature prediction (± 10 K) would not have been achievable. The applied codes for mechanical fuel behaviour largely demonstrated their capabilities for pretest-predictions. It was the opinion of all participants that for the time being a coupled Standard Problem Activity (Integral prediction of thermohydraulics and fuel behaviour) in this field would have been without success due to the expected large uncertainty-band of thermohydraulic pretest-predictions. (orig./HP)